A system for determining a drowsy state of a driver includes: a heartbeat measurement module configured to detect a heartbeat rate of the driver and output a heartbeat signal corresponding to the detected heartbeat rate; a vehicle signal measurement module configured to measure a driving state of a vehicle being driven by the driver and output a vehicle signal corresponding to the measured driving state; a drowsy pattern detection module configured to determine whether a driver has fallen asleep while driving based on the heartbeat signal and the vehicle signal and output a warning signal as a drowsy warning in response to determining that the driver has fallen asleep while driving; and a warning module configured to output a warning to the driver based on the warning signal.